Method for preparing superfine iron powder by using steel mill pickling iron oxide powder
By utilizing a low-temperature reduction method using pickled iron oxide powder from steel mills and plasma-state hydrogen reducing agent, combined with a dedicated reduction device and inert protection, the problems of high energy consumption and low efficiency of traditional reduction methods have been solved. This significantly improves reduction efficiency and product purity, simplifies the process flow, and achieves the effect of preparing ultrafine iron powder with high efficiency and low cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHIJIAZHUANG CENSHUN MAGNETIC TECH CO LTD
- Filing Date
- 2026-02-09
- Publication Date
- 2026-05-05
AI Technical Summary
Traditional reduction methods for preparing ultrafine iron powder are energy-intensive, have low reduction efficiency, and require secondary reduction treatment, leading to increased production costs and increased process complexity.
Using pickled iron oxide powder from steel mills as raw material, combined with plasma hydrogen reducing agent and a dedicated reduction device, the raw material waste heat is used for low-temperature reduction. The screw feeding and sonic stirring ensure full contact, and subsequent magnetic separation and airflow classification treatment form an inert protective atmosphere.
It significantly reduced the reduction temperature and energy consumption, improved the reduction efficiency and product purity, simplified the process flow, and reduced production costs.
Smart Images
Figure CN121972673A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills. Background Technology
[0002] As an important functional metal material, ultrafine iron powder has shown broad application prospects in many high-tech fields such as powder metallurgy, magnetic materials, superhard materials, catalysts, and precision chemicals due to its unique physicochemical properties. With the rapid development of related industries, the market demand for ultrafine iron powder has continued to grow steadily, and the requirements for its preparation quality and production efficiency have also been continuously improved.
[0003] Currently, the main industrial methods for preparing ultrafine iron powder include reduction, electrolysis, and atomization. Among these, reduction has become one of the mainstream methods for preparing ultrafine iron powder due to its mature technology, wide availability of raw materials, and relatively controllable production costs, and it has been widely used in industrial production.
[0004] However, traditional reduction methods for preparing ultrafine iron powder still have many technical shortcomings that need to be addressed. The process typically uses hydrogen as a reducing agent, and the reduction equipment often employs pusher kilns or tunnel kilns. During reduction, iron oxide powder must be loaded into a bowl before being fed into the kiln for the reduction reaction. Furthermore, to achieve the required quality of ultrafine iron powder, secondary or even tertiary reduction treatments are often necessary. Moreover, the resulting high-quality ultrafine iron powder typically has a particle size of 500 mesh and a purity of around 97%.
[0005] The shortcomings of the aforementioned traditional process are mainly reflected in the following two aspects: Firstly, the hydrogen reduction reaction requires a high temperature, usually above 900℃. This excessively high reaction temperature leads to a significant increase in energy consumption during production, raising production costs and contradicting the current trend of energy conservation and environmental protection in industrial development. Secondly, because the iron oxide powder is placed in a bowl, hydrogen cannot effectively penetrate the material during reduction, only reducing the shallow surface layer. An effective reducing atmosphere cannot be formed deep within the material, resulting in incomplete reduction and low efficiency. To overcome this deficiency, the existing process requires crushing the initial reduction product under nitrogen protection before a secondary reduction. This not only increases the number of process steps, making the entire preparation process more complex, but also further increases energy consumption and production costs, limiting the large-scale and efficient development of the ultrafine iron powder industry. Summary of the Invention
[0006] This invention provides a method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills, aiming to solve the technical problems described in the background section above.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills, comprising the following steps: S01, pickled iron oxide powder from the bottom of the acid regeneration spray roasting furnace of the steel plant is selected as raw material, and the pickled iron oxide powder is kept warm and transported to the reduction device. S02, after the pickled iron oxide powder is heated to the reduction temperature by the reduction device, plasma hydrogen is introduced into the reduction device as a reducing agent, and the pickled iron oxide powder and plasma hydrogen complete the reduction reaction to generate iron powder under stirring conditions. S03, after the reduction reaction, the iron powder is cooled, magnetically separated and purified, and air classified to obtain the ultrafine iron powder product; nitrogen is introduced during the discharge and finished product packaging process to form an inert protective atmosphere to prevent the ultrafine iron powder from oxidizing. S04, the incompletely reduced oxidized impurities separated during the magnetic separation purification process are transported back to the reduction device for a new reduction reaction.
[0008] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, in step S01, the pickled iron oxide powder at the bottom of the regenerated spray roasting furnace is conveyed to the reduction device in a heat-insulating conveying device. The heat-insulating conveying device includes a feeding device and a heat-insulating layer disposed on the feeding device; The residual heat generated at the bottom of the acid regeneration spray roasting furnace by pickling iron oxide powder ensures that the raw material temperature is not lower than 350℃ when it is transported to the reduction unit.
[0009] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, the feeding device is a screw feeder with a conveying speed of 0.2~0.5m / s; the insulation layer is a rock wool insulation layer with a thickness of 60~100mm.
[0010] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, in step S02, the reduction device is an electromagnetically heated rotary kiln with internal spiral blades; the reduction temperature is 500~600℃, achieved by supplementing heating with residual heat from the raw materials using an electromagnetic heating device; the plasma hydrogen is prepared by a plasma generator with a power of 5-10kW, and the flow rate of the plasma hydrogen is 2~5m³ / h.
[0011] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, the material flow is driven by an inner spiral blade, and the stirring conditions are achieved by sound waves generated by a sound wave generator, so that the pickled iron oxide powder and plasma hydrogen are in full contact; the rotation speed of the reduction device is 2~4 r / min, and the residence time of the material in the reduction device is 1.5~3h.
[0012] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, the pitch of the inner spiral blade is 200~300mm, and the acoustic wave generator generates acoustic waves of 20~50kHz.
[0013] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, in step S03, the cooling is carried out by air cooling to room temperature; the magnetic separation purification is carried out by a permanent magnet separator with a magnetic separation intensity of 800-1200 Gs; the air classification is carried out by a horizontal air classifier with a classifying airflow velocity of 8-12 m / s and a classifying particle size controlled at 1-10 μm.
[0014] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, in step S03, the nitrogen flow rate at the discharge port is 1~3 m³ / h, and the nitrogen charging pressure during finished product packaging is 0.1-0.2 MPa, so as to effectively prevent iron powder oxidation.
[0015] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by the present invention, in step S04, the incompletely reduced oxide impurities are transported back to the reduction device through an inert conveying channel.
[0016] Specifically, inert conveying channels are achieved by introducing inert gases such as nitrogen into the conveying channels of existing conveying devices (such as screw conveyors, belt conveyors, etc.).
[0017] In one possible implementation of the method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant provided by the present invention, the inert conveying channel is achieved by introducing an inert gas into the conveying channel.
[0018] The beneficial effects of the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by this invention are as follows: Compared with the prior art, the method for preparing ultrafine iron powder using pickled iron oxide powder from steel mills provided by this invention fully utilizes the unique characteristics of pickled iron oxide powder from steel mills, such as fine particle size, high surface activation energy, low reduction temperature, and residual heat carried by the furnace bottom generation temperature of 400-500℃. Combined with the advantage of strong reducibility of plasma hydrogen, it realizes the recovery and utilization of residual heat and low-temperature reduction. Compared with the traditional hydrogen reduction process, the reduction temperature is reduced by 300-400℃, significantly reducing energy consumption and achieving significant energy-saving effect.
[0019] Raw materials are directly conveyed from the bottom of the acid regeneration spray roasting furnace by a screw feeder, reducing material transfer links, reducing waste heat loss and dust pollution during the transfer process, and effectively realizing the recovery and utilization of waste heat.
[0020] An electromagnetically heated rotary kiln with internal spiral blades is used as the reduction device, replacing the traditional pusher kiln and tunnel kiln. It eliminates the need for a boat-shaped container to hold the material. Combined with sonic stirring, it significantly increases the contact area and uniformity between plasma hydrogen and iron oxide powder, ensuring sufficient reduction. This effectively solves the defects of traditional processes where the boat-shaped container leads to incomplete hydrogen reduction and the need for secondary reduction. At the same time, the internal spiral blades allow the iron oxide powder to flow smoothly in the kiln, effectively avoiding dust pollution caused by material falling and significantly improving the reaction rate and reduction rate.
[0021] By setting up a cyclic reduction process, the incompletely reduced oxide impurities are fed back into the reduction kiln for a secondary reaction, further improving the utilization rate of raw materials; the subsequent magnetic separation purification and airflow classification treatment ensure the purity and particle size accuracy of the ultrafine iron powder product. Attached Figure Description
[0022] Figure 1 This is a schematic flowchart of a method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant, provided in an embodiment of the present invention. Detailed Implementation
[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.
[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is actually illustrative only and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.
[0027] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.
[0028] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, and the spatial relative descriptions used herein will be interpreted accordingly.
[0029] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.
[0030] It should be noted that the inventors, while researching steel mill pickling iron oxide powder, discovered that it possesses unique physicochemical properties: firstly, it has fine particle size, high surface activation energy, and a lower reduction temperature than ordinary iron oxide powder; secondly, the furnace bottom generation temperature of this pickling iron oxide powder is 400-500℃, inherently carrying a certain amount of residual heat potential. Simultaneously, plasma hydrogen has stronger reducing properties than ordinary hydrogen, enabling efficient reduction of iron oxide powder at lower temperatures. Based on these characteristics, if waste heat utilization and low-temperature reduction technology can be combined, along with dedicated reduction reaction facilities, the energy consumption and cost of preparing ultrafine iron powder can be significantly reduced.
[0031] Please see Figure 1 The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.
[0032] Example 1 A method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant includes the following steps: S01, pickled iron oxide powder from the bottom of the acid regeneration spray roasting furnace of the steel plant is selected as raw material. The pickled iron oxide powder is directly conveyed from the bottom of the acid regeneration spray roasting furnace (the furnace bottom temperature is above 400°C) to the electromagnetic heating rotary kiln with inner spiral blades by a shaftless screw conveyor (conveyor speed 0.2m / s). A 60mm thick rock wool insulation layer is set on the outer layer of the shaftless screw conveyor to achieve heat preservation during conveying. The raw material temperature is 360°C when it is conveyed to the reduction unit.
[0033] S02, start the electromagnetically heated rotary kiln with internal spiral blades, and introduce the pickled iron oxide powder from the shaftless screw conveyor into the kiln; start the electromagnetic heating device, and combine it with the residual heat of the raw materials to supplement the kiln temperature to 500℃; introduce plasma hydrogen prepared by a plasma generator (power 5kW) into the kiln as a reducing agent, and control the plasma hydrogen flow rate to 2m³ / h; control the rotary kiln speed to 2r / min, and the internal spiral blade pitch to 200mm, so that the pickled iron oxide powder can flow smoothly in the kiln through the internal spiral blades; at the same time, start the sonic generators set in the middle and tail of the rotary kiln to generate sound waves with a frequency of 20kHz to stir the material in the kiln, control the residence time of the material in the kiln to 3h, and complete the reduction reaction to generate iron powder without secondary reduction.
[0034] S03, the iron powder after reduction reaction is cooled to room temperature by air cooling, and then a permanent magnet magnetic separator is used to remove incompletely reduced oxide impurities. The magnetic separation intensity is 800 Gs. Then, it is subjected to air classification by a horizontal air classifier (classification airflow velocity 8 m / s) to control the classification particle size to 1-10 μm, so as to obtain ultrafine iron powder product. The nitrogen protection device is turned on at the discharge port of the electromagnetic heating rotary kiln, and nitrogen gas is introduced into the discharge area (introduction flow rate 1 m³ / h) to form an inert protective atmosphere. In the finished product packaging stage, a nitrogen-filled packaging device is used to fill the packaging container with nitrogen gas (filling pressure 0.1 MPa) to replace the air before sealing.
[0035] S04, the incompletely reduced oxidized impurities separated during the magnetic separation purification process, is transported back to the electromagnetically heated rotary kiln with spiral blades inside the belt through an inert conveying channel for a new reduction reaction.
[0036] The ultrafine iron powder product has a purity of 99.6%, a particle size of 2030 mesh, a total raw material utilization rate of 98.6%, and an oxidation rate of less than 0.5% after 3 months of storage.
[0037] Example 2 A method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant includes the following steps: S01, pickled iron oxide powder from the bottom of the acid regeneration spray roasting furnace of the steel plant is selected as raw material. The pickled iron oxide powder is directly transported from the bottom of the acid regeneration spray roasting furnace to the electromagnetic heating rotary kiln with internal spiral blades by a shaftless screw conveyor (conveying speed 0.35m / s). The shaftless screw conveyor is equipped with an 80mm thick rock wool insulation layer to achieve heat preservation during transportation. The raw material temperature is 380℃ when it is transported to the reduction unit.
[0038] S02, start the electromagnetically heated rotary kiln with internal spiral blades, and introduce the pickled iron oxide powder from the shaftless screw conveyor into the kiln; start the electromagnetic heating device, and combine it with the residual heat of the raw materials to supplement the kiln temperature to 550℃; introduce plasma hydrogen prepared by a plasma generator (power 8kW) into the kiln as a reducing agent, and control the plasma hydrogen flow rate to 3.5m³ / h; control the rotary kiln speed to 3r / min, and the internal spiral blade pitch to 250mm, so that the pickled iron oxide powder can flow smoothly in the kiln through the internal spiral blades; at the same time, start the sonic generators set in the middle and tail of the rotary kiln to generate sound waves with a frequency of 35kHz to stir the material in the kiln, control the residence time of the material in the kiln to 2.2h, and complete the reduction reaction to produce iron powder without secondary reduction.
[0039] S03, the iron powder after reduction reaction is cooled to room temperature by air cooling, and then a permanent magnet magnetic separator is used to remove incompletely reduced oxide impurities. The magnetic separation intensity is 1000 Gs. Then, it is subjected to air classification by a horizontal air classifier (classification airflow velocity 10 m / s) to control the classification particle size to 1-10 μm, so as to obtain ultrafine iron powder product. The nitrogen protection device is turned on at the discharge port of the electromagnetic heating rotary kiln, and nitrogen gas is introduced into the discharge area (introduction flow rate 2 m³ / h) to form an inert protective atmosphere. In the finished product packaging stage, a nitrogen-filled packaging device is used to fill the packaging container with nitrogen gas (filling pressure 0.15 MPa) to replace the air before sealing.
[0040] S04, the incompletely reduced oxidized impurities separated during the magnetic separation purification process, is transported back to the electromagnetically heated rotary kiln with spiral blades inside the belt through an inert conveying channel for a new reduction reaction.
[0041] The ultrafine iron powder product has a purity of 99.7%, a particle size of 2015 mesh, a total raw material utilization rate of 99.0%, and an oxidation rate of less than 0.3% after 3 months of storage.
[0042] Example 3 A method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant includes the following steps: S01, pickled iron oxide powder from the bottom of the acid regeneration spray roasting furnace of the steel plant is selected as raw material. The pickled iron oxide powder is directly transported from the bottom of the acid regeneration spray roasting furnace to the electromagnetic heating rotary kiln with internal spiral blades by a shaftless screw conveyor (conveying speed 0.5m / s). A 100mm thick rock wool insulation layer is set on the outer layer of the shaftless screw conveyor to achieve heat preservation during transportation. The raw material temperature is 400℃ when it is transported to the reduction unit.
[0043] S02, start the electromagnetically heated rotary kiln with internal spiral blades, and introduce the pickled iron oxide powder from the shaftless screw conveyor into the kiln; start the electromagnetic heating device, and combine it with the residual heat of the raw materials to supplement the kiln temperature to 600℃; introduce plasma hydrogen prepared by a plasma generator (power 10kW) into the kiln as a reducing agent, and control the plasma hydrogen flow rate to 5m³ / h; control the rotary kiln speed to 4r / min, and the internal spiral blade pitch to 300mm, so that the pickled iron oxide powder can flow smoothly in the kiln through the internal spiral blades; at the same time, start the sonic generators set in the middle and tail of the rotary kiln to generate sound waves with a frequency of 50kHz to stir the material in the kiln, control the residence time of the material in the kiln to 1.5h, and complete the reduction reaction to produce iron powder without secondary reduction.
[0044] S03, the iron powder after reduction reaction is cooled to room temperature by air cooling, and then a permanent magnet magnetic separator is used to remove incompletely reduced oxide impurities. The magnetic separation intensity is 1200Gs. Then, it is subjected to air classification by a horizontal air classifier (classification airflow velocity 12m / s) to control the classification particle size to 1-10μm, so as to obtain ultrafine iron powder product. The nitrogen protection device is turned on at the discharge port of the electromagnetic heating rotary kiln, and nitrogen gas is introduced into the discharge area (introduction flow rate 3m³ / h) to form an inert protective atmosphere. In the finished product packaging stage, a nitrogen-filled packaging device is used to fill the packaging container with nitrogen gas (filling pressure 0.2MPa) to replace the air before sealing.
[0045] S04, the incompletely reduced oxidized impurities separated during the magnetic separation purification process, is transported back to the electromagnetically heated rotary kiln with spiral blades inside the belt through an inert conveying channel for a new reduction reaction.
[0046] Tests showed that the purity of the ultrafine iron powder product was 99.5%, the particle size was 1190 mesh, the total utilization rate of raw materials was 98.8%, and the oxidation rate of the finished product was less than 0.4% after 3 months of storage.
[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant, characterized in that, Includes the following steps: S01, pickled iron oxide powder from the bottom of the acid regeneration spray roasting furnace of the steel plant is selected as raw material, and the pickled iron oxide powder is kept warm and transported to the reduction device. S02, after the pickled iron oxide powder is heated to the reduction temperature by the reduction device, plasma hydrogen is introduced into the reduction device as a reducing agent, and the pickled iron oxide powder and plasma hydrogen complete the reduction reaction to generate iron powder under stirring conditions. S03, the iron powder after reduction reaction is cooled, magnetically separated and purified, and air classified to obtain ultrafine iron powder product; nitrogen is introduced during the discharge and finished product packaging process to form an inert protective atmosphere; S04, the incompletely reduced oxidized impurities separated during the magnetic separation purification process are transported back to the reduction device for a new reduction reaction.
2. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 1, characterized in that, In step S01, the pickled iron oxide powder from the bottom of the regenerated spray roasting furnace is conveyed to the reduction device in a heated manner using a heat-insulating conveying device. The heat-insulating conveying device includes a feeding device and a heat-insulating layer disposed on the feeding device; The residual heat generated at the bottom of the acid regeneration spray roasting furnace by pickling iron oxide powder ensures that the raw material temperature is not lower than 350℃ when it is transported to the reduction unit.
3. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 2, characterized in that, The feeding device is a screw feeder with a conveying speed of 0.2~0.5m / s; the insulation layer is a rock wool insulation layer with a thickness of 60~100mm.
4. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 1, characterized in that, In step S02, the reduction device is an electromagnetically heated rotary kiln with internal spiral blades; the reduction temperature is 500~600℃, which is achieved by combining electromagnetic heating device with residual heat of raw materials for supplementary heating; the plasma hydrogen is prepared by plasma generator, and the flow rate of plasma hydrogen is 2~5m³ / h.
5. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 4, characterized in that, The material is driven to flow by the inner spiral blades, and the stirring conditions are achieved by the sound waves generated by the sound wave generator; the rotation speed of the reduction device is 2~4 r / min, and the residence time of the material in the reduction device is 1.5~3h.
6. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 5, characterized in that, The pitch of the inner helical blade is 200~300mm, and the sound wave generator produces sound waves of 20~50kHz.
7. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 1, characterized in that, In step S03, the cooling is achieved by air cooling to room temperature; the magnetic separation purification is achieved by a permanent magnet separator; and the airflow classification is achieved by a horizontal airflow classifier with a classification airflow velocity of 8~12m / s and a classification particle size of 1~10μm.
8. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 1, characterized in that, In step S03, the nitrogen flow rate at the outlet is 1~3 m³ / h, and the nitrogen filling pressure during finished product packaging is 0.1-0.2 MPa.
9. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 1, characterized in that, In step S04, the incompletely reduced oxidized impurities are transported back to the reduction device through an inert transport channel.
10. The method for preparing ultrafine iron powder using pickled iron oxide powder from a steel plant as described in claim 9, characterized in that, The inert transport channel is achieved by introducing inert gas into the transport channel.